A road finisher comprising a height adjusting device of this type is disclosed in DE 29505382 U1. It comprises a basic screed plate and two extendable screed plates that can be hydraulically extended parallel to the basic screed plate for the purpose of broadening the work area. The basic screed plate and the extendable screed plates comprise ground elements, of which each is provided with a base plate on its underside. The extendable screed plates are mounted on the basic screed plate for vertical adjustment thereon, so that their base plates can be adjusted and moved to a specified position relative to the base plates of the basic screed plate. To this end, each ground element of the extendable screed plates is provided with two pairs of adjusting members on the main screed plate, these being located in the region of the two end faces of each extendable screed plate. The adjusting members are in the form of screws or screw-threaded spindles disposed at one end on the ground element and at the other end on, in each case, a leg of a toggle joint. The other two legs of the toggle joint of a pair are further interconnected via a linkage system such that both toggle joints can be actuated concurrently for the purpose of altering the height of the relevant side of the ground element relatively to the basic screed plate.
A drawback of this arrangement may be considered to be the fact that the toggle joint and the linkage system are required to absorb the weight of the respective ground element. They, therefore, have to be appropriately bulky and are, therefore, relatively expensive.
In order to alter the thickness of the layer of material being filled in and for adaptation to the consistency thereof, it is important that it be also possible to change the setting angle of the ground element. The setting angle, which may also be referred to as the adjusted angle, is the angle between the base plate and the ground as regarded in the direction of travel. A regulating device for the setting angle is disclosed in DE 9211854 U1. An adjustment of the setting angle accordingly takes place in that that adjusting member of a pair which is adjacent to the basic screed plate is displaced, while the other adjusting member of said pair remains unchanged.
It is an object of the present invention to provide a height adjusting device and a road finisher of the kind defined above, in which the actuator used is inexpensive and which makes it possible to adjust the setting angle in a simple manner.